Strengthening ribs on corrugated containers for bulk materials are desirable for bulge resistance and stacking strength, and are known in the prior art.
In U.S. Pat. No. 3,097,781 which issued July 16, 1963 to J. J. Masi, there is disclosed a paper board container with internally projecting, vertically disposed, triangular shaped reinforcing posts, integral with the side wall. However, this design places the support posts near the corners of the box, where they are least effective to provide bulge resistance. Furthermore, the Masi patent provides for the construction of the four side walls from three pieces of paper board, and requires a complicated construction procedure. U.S. Pat. Nos. 4,081,124 issued Mar. 28, 1978 to D. Y. Hall, and 3,159,326, issued Dec. 1, 1964 to D. A. Stonebanks, also disclose fiber board containers with inwardly projecting vertically disposed triangular shaped reinforcing posts. In these designs the reinforcing post is formed from a vertical fold in the middle of a side wall, not involving an end of a side wall. Some means, such as the jig disclosed in U.S. Pat. No. 4,081,124, must be provided to hold the side walls in this folded configuration during construction of the box.
There is a need for a reinforced corrugated container for bulk materials, which can be easily manufactured and erected from a small number of corrugated parts.